Heretofore, there has been a problem that, due to vibration of an article, such as a spare tire, during running of a vehicle, an article storage portion, such as a spare tire pan, supporting and fixing the article, is vibrated (primarily, vibrated in an up-down direction) to enter into resonance together with a surrounding region, thereby generating noise, such as muffled sound within a passenger compartment (ear-oppressing sound of a bandwidth from 20 to 300 Hz), and giving a passenger a discomfort feeling.
In order to solve this problem, vehicle body floor panel structures disclosed in the following Japanese references JP 2010-221877A and JP 2000-255455A have already been proposed.
In the structure disclosed in the JP 2010-221877A, in order to allow an article such as a tire to be spaced apart from a floor panel forming an article storage portion (tire hosing), an article holding portion such as a rear floor cross member is disposed to extend between right and left rear side frames each located on a respective one of opposite sides of and above the article storage portion, and used to allow an article such as a tire to be pulled upwardly away from the floor panel, thereby shifting a resonant frequency of the floor panel out of a low frequency band during vehicle running, to reduce noise due to vibration of the article storage portion.
However, the conventional structure disclosed in the JP 2010-221877A additionally requires the article holding portion such as a rear floor cross member, so that a vehicle body weight is increased. This has an advantage of being able to achieve a reduction in noise, on the other hand, has a problem that a reduction in vehicle body weight is hindered.
In the structure disclosed in the JP 2000-255455A, a rear cross member and a reinforcing rib are provided underneath a rear floor panel comprising an article storage portion (tire well), to enhance rigidity of the article storage portion, thereby preventing occurrence of vibration and abnormal noise to improve ride quality of the vehicle.
However, the conventional structure disclosed in the JP 2000-255455A also has a problem of an increase in vehicle body weight, due to a need for an additional member such as the rear cross member and the reinforcing rib.